Walse et al. disclosed a low insertion force electrical connector in their U.S. Pat. No. 4,575,172 by inserting a printed circuit board into a C-shaped portion 70 with two opposed arcuate beam members 72, 74 for clamping the printed circuit board. The C-shaped portion 70 requires further means for preventing the overstressing of beam members 72, 74 beyond their intended limits as mentioned in their original specification. So upon an insertion of the board 12, the C-shaped portion will be subjected to an internal stress acting thereon causing permanent set of the contact elements and poor electrical connection since the C-shaped portion is lacking of any means for releasing the stress.
U.S. Pat. No. 4,737,120 of Grabbe et al. disclosed an electrical connector having a contact 36 for connecting the daughter board 18 with the mother board 34, including a spring 68 for resiliently clamping the board 18 by the two contact portions 66, 50. Since the spring 68 is adjacent to the right contact portion 66, a single side resilience force will act upon the right-leaf contact portion 66 to unbalancedly bias the upper projection 72 of the right contact portion 66 against the lower projection 60 of the left contact portion 50, causing a great bending moment and internal stress in the contact 36. The integral contact 36 is not provided with efficient means for releasing such a stress, thereby still easily causing deformation of the contact elements and poor electrical connection.
The present inventor has found the drawbacks of the conventional electrical connector, and invented the present contact element capable of self-compensation for its internal stress for a satisfactory use in an electrical connector.